Articles (Science)

Swimming hundreds of feet beneath the ocean’s surface in many parts of the world are prolific architects called giant larvaceans. These zooplankton are not particularly giant themselves (they resemble tadpoles and are about the size of a pinkie finger), but every day, they construct one or more spacious houses” that can exceed three feet in length. The houses are transparent mucus structures that encase the creatures inside. Giant larvaceans beat their tails to pump seawater through these structures, which filter tiny bits of dead or drifting organic matter for the animals to eat. When their filters get clogged, the larvaceans abandon ship and construct a new house. Laden with debris from the water column, old houses rapidly sink to the seafloor. In a study published in Science Advances on Wednesday, scientists near California’s Monterey Bay have found that, through this process, giant larvaceans can filter all of the bay’s water from about 300 to 1,000 feet deep in less than two weeks, making them the fastest known zooplankton filter feeders. In doing so, the creatures help transfer carbon that has been removed from the atmosphere by photosynthesizing organisms to the deep sea, where it can be buried and stored long term. And given their abundance in other parts of the world, these organisms likely play a crucial role in the global carbon cycle. When it comes to the flow of carbon in the ocean, we don’t know nearly as much as we should,” said Kakani Katija, a principal engineer at the Monterey Bay Aquarium Research Institute and the study’s lead author. If we really want to understand how the system works, we have to look at all the players involved. Giant larvaceans are one important group we need to learn more about.” In the past, other scientists have tried studying giant larvaceans in the laboratory. But these efforts always failed because the animals’ houses were too fragile to be harvested and collected specimens were never able to build houses outside the ocean.To study the zooplankton in their natural habitat, Dr. Katija and her collaborators developed a new deep-sea imaging instrument, called DeepPIV, which they paired with a remotely operated vehicle. DeepPIV projects a sheet of laser light that cuts straight through a larvacean’s mucus house. A high-definition camera on the remotely operated vehicle can then capture the inner pumping mechanisms illuminated by the laser.

The recording starts with the patter of a summer squall. Later, a drifting tone like that of a not-quite-tuned-in radio station rises and for a while drowns out the patter. These are the sounds encountered by NASA’s Cassini spacecraft as it dove through the gap between Saturn and its innermost ring on April 26, the first of 22 such encounters before it will plunge into Saturn’s atmosphere in September. What Cassini did not detect were many of the collisions of dust particles hitting the spacecraft as it passed through the plane of the rings. You can hear a couple of clicks,” said William S. Kurth, a research scientist at the University of Iowa who is the principal investigator for Cassini’s radio and plasma science instrument. The few dust hits that were recorded sounded like the small pops caused by dust on a LP record, he said. What he had expected was something more like the din of driving through Iowa in a hailstorm,” Dr. Kurth said. Since Cassini had not passed through this region before, scientists and engineers did not know for certain what it would encounter. Cassini would be traveling at more than 70,000 miles per hour as it passed within 2,000 miles of the cloud tops, and a chance hit with a sand grain could be trouble. The analysis indicated that the chances of such a collision were slim, but still risky enough that mission managers did not send Cassini here until the mission’s final months. As a better-safe-than-sorry precaution, the spacecraft was pointed with its big radio dish facing forward, like a shield. Not only was there nothing catastrophic, there was hardly anything at all. The few clicking sounds were generated by dust the size of cigarette smoke particles about a micron, or one-25,000th of an inch, in diameter. To be clear: Cassini did not actually hear any sounds. It is, after all, flying through space where there is no air and thus no vibrating air molecules to convey sound waves. But space is full of radio waves, recorded by Dr. Kurth’s instrument, and those waves, just like the ones bouncing through the Earth’s atmosphere to broadcast the songs of Bruno Mars, Beyoncé and Taylor Swift, can be converted into audible sounds. Dr. Kurth said the background patter was likely oscillations of charged particles in the upper part of Saturn’s ionosphere where atoms are broken apart by solar and cosmic radiation. The louder tones were almost certainly whistler mode emissions” when the charged particles oscillate in unison.

MIAMI — For decades, South Florida schoolchildren and adults fascinated by far-off galaxies, earthly ecosystems, the properties of light and sound and other wonders of science had only a quaint, antiquated museum here in which to explore their interests. Now, with the long-delayed opening of a vast new science museum downtown set for Monday, visitors will be able to stand underneath a suspended, 500,000-gallon aquarium tank and gaze at hammerhead and tiger sharks, mahi mahi, devil rays and other creatures through a 60,000-pound oculus, a lens that will give the impression of seeing the fish from the bottom of a huge cocktail glass. And that’s just one of many attractions and exhibits. Officials at the $305 million Phillip and Patricia Frost Museum of Science promise that it will be a vivid expression of modern scientific inquiry and exposition. Its opening follows a series of setbacks and lawsuits and a scramble to finish the 250,000-square-foot structure. At one point, the project ran precariously short of money. The museum’s high-profile opening is especially significant in a state imperiled by rising sea levels and overseen by a governor, Rick Scott, who has said he is unconvinced that climate change and global warming are real and whose administration is widely reported to have set an unwritten policy that state agencies refrain from using the terms. The problem is not that people don’t believe in science, but that they pick and choose which science they want to believe,” Frank Steslow, a microbiologist appointed a year ago as the museum’s president, said on a recent morning while walking around the four-acre site. I don’t know that we need to do anything other than be who we are and present the facts and be a resource for everybody.” As workers swarmed over the site — near the Pérez Art Museum Miami and the Adrienne Arsht Center for the Performing Arts — Mr. Steslow pointed to interactive exhibits about the fragile South Florida ecosystem, including one on the vast but shrinking Everglades wetlands, and the varied animal species, many of them endangered, that call the region home.

Mauna Loa, the biggest volcano on Earth — and one of the most active — covers half the Island of Hawaii. Just 35 miles to the northeast, Mauna Kea, known to native Hawaiians as Mauna a Wakea, rises nearly 14,000 feet above sea level. To them it represents a spiritual connection between our planet and the heavens above. These volcanoes, which have beguiled millions of tourists visiting the Hawaiian islands, have also plagued scientists with a long-running mystery: If they are so close together, how did they develop in two parallel tracks along the Hawaiian-Emperor chain formed over the same hot spot in the Pacific Ocean — and why are their chemical compositions so different? We knew this was related to something much deeper, but we couldn’t see what,” said Tim Jones, an earth science Ph.D. student at Australian National University and the lead author of a paper published in Nature on Wednesday that may hold the answer. Mr. Jones and his colleagues developed a model that simulates what’s happening in our planet’s mantle, beneath the crust that we live on, offering a window to the center of the Earth — or close to it. Their study may one day allow a reconstruction of the history of the movement of Earth’s plates — and the processes linked to these movements over billions of years, like mass extinction events, diamond and oil deposits, and changes in climate. If you were to drill nearly 4,000 miles into the Earth, you’d reach its core, a ball of solid iron surrounded by liquid that scientists estimate is hotter than the sun. Before making it there, you’d hit the mantle — an 1,800-mile-thick layer of solid rock that can flow like a liquid, just substantially slower. This mantle is the reason plates move across the surface. It’s why we have continents, earthquakes and volcanoes. The closest anyone ever got to the mantle was a seven-mile-deep hole drilled into the crust on a peninsula in western Russia. But now we can better understand what’s happening below by looking at Mauna Kea and Mauna Loa, said Mr. Jones. The prevailing hypothesis has been that volcanoes like these two in Hawaii are chemical fingerprints of the Earth’s composition at the deep mantle, just at the border of its core. Scientists have seismic evidence that the deep part of the mantle is a graveyard where long ago slabs of earth were subducted, or thrust underneath one another, creating separate regions with different chemical compositions that eventually made their way to the surface in a hot mantle plume, or upwelling, as the core heated the rock into magma.But that didn’t explain the separate tracks along which the volcanoes formed. By examining data from the two volcanoes, Mr. Jones and his team suggested an alternative: The chemical signature, along with this double-track volcanism as it’s called, occurred three million years ago when the plates above the hot spot shifted direction, moving north. This shimmy rearranged zones of magma that are heated under different pressures in the shallower part of the mantle — when they cool, the volcanic rock that results reflects this difference. Previously stacked on top of one another, the movement of the plates exposed now geographically separates magma zones that fed the volcanoes individually.

Sifting through teaspoons of clay and sand scraped from the floors of caves, German researchers have managed to isolate ancient human DNA — without turning up a single bone. Their new technique, described in a study published on Thursday in the journal Science, promises to open new avenues of research into human prehistory and was met with excitement by geneticists and archaeologists. It’s a bit like discovering that you can extract gold dust from the air,” said Adam Siepel, a population geneticist at Cold Spring Harbor Laboratory.An absolutely amazing and exciting paper,” added David Reich, a genetics professor at Harvard who focuses on ancient DNA. Until recently, the only way to study the genes of ancient humans like the Neanderthals and their cousins, the Denisovans, was to recover DNA from fossil bones. But they are scarce and hard to find, which has greatly limited research into where early humans lived and how widely they ranged. The only Denisovan bones and teeth that scientists have, for example, come from a single cave in Siberia. Looking for these genetic signposts in sediment has become possible only in the last few years, with recent developments in technology, including rapid sequencing of DNA. Although DNA sticks to minerals and decayed plants in soil, scientists did not know whether it would ever be possible to fish out gene fragments that were tens of thousands of years old and buried deep among other genetic debris. Bits of genes from ancient humans make up just a minute fraction of the DNA floating around in the natural world. But the German scientists, led by Matthias Meyer at the Max Planck Institute for Developmental Biology in Tübingen, have spent years developing methods to find DNA even where it seemed impossibly scarce and degraded. There’s been a real revolution in technology invented by this lab,” Dr. Reich said. Matthias is kind of a wizard in pushing the envelope.” Scientists began by retrieving DNA from ancient bones: first Neanderthals, then Denisovans. To identify the Denisovans, Svante Paabo, a geneticist at the Planck Institute and a co-author of the new paper, had only a child’s pinkie bone to work with. His group surprised the world in 2010 by reporting that it had extracted DNA from the bone, finding that it belonged to a group of humans distinct from both Neanderthals and modern humans. But that sort of analysis is limited by the availability of fossil bones. In a lot of cases, you can get bones, but not enough,” said Hendrik Poinar, an evolutionary geneticist at McMaster University. If you just have one small piece of bone from one site, curators do not want you to grind it up.”